If you're looking for a new challenge to an old standby exercise, the 3x3 pull-up protocol delivers big and will challenge you in different ranges of the movement.
If you're able to complete all 3 reps of this monster (9 partial reps), simply add some external load using a weight vest or dip belt.
Keep in mind that you can do this protocol in a chin-up (underhand) grip or neutral grip as well.